Islam M S, Berggren P O, Larsson O
Rolf Luft Center for Diabetes Research, Department of Endocrinology, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden.
FEBS Lett. 1993 Mar 15;319(1-2):128-32. doi: 10.1016/0014-5793(93)80051-u.
Effects of sulfhydryl modification on the ATP regulated K+ channel (KATP channel) in the pancreatic beta-cell were studied, using the patch clamp technique. Application of the sulfhydryl oxidizing agents thimerosal and 2,2'-dithio-bis(5-nitropyridine) (DTBNP), in micromolar concentrations, caused complete inhibition of the KATP channel, in inside-out patches. The inhibition was rapid and was reversed by the disulfide reducing agents dithiothreitol and cysteine. Thimerosal, which is poorly membrane permeable, inhibited channel activity, only when applied to the intracellular face of the plasma membrane. In contrast, DTBNP, which is highly lipophilic, caused closure of the KATP channel and consequent depolarization of the membrane potential, also when applied extracellularly. Our results indicate the presence of accessible free SH groups on the cytoplasmic side of the KATP channel in the pancreatic beta-cell. These SH groups are essential for channel function and it is possible that thiol-dependent redox mechanisms can modulate KATP channel activity.
采用膜片钳技术研究了巯基修饰对胰腺β细胞中ATP调节钾通道（KATP通道）的影响。在膜内面向外的膜片中，微摩尔浓度的巯基氧化剂硫柳汞和2,2'-二硫代双（5-硝基吡啶）（DTBNP）可完全抑制KATP通道。抑制作用迅速，且可被二硫键还原剂二硫苏糖醇和半胱氨酸逆转。硫柳汞的膜通透性较差，只有在应用于质膜的细胞内面时才会抑制通道活性。相比之下，具有高亲脂性的DTBNP，在细胞外应用时也会导致KATP通道关闭并随之引起膜电位去极化。我们的结果表明，胰腺β细胞中KATP通道的胞质侧存在可及的游离巯基。这些巯基对于通道功能至关重要，并且硫醇依赖性氧化还原机制有可能调节KATP通道活性。
